The Spartan army stood at the center of the Spartan state, citizens trained in the disciplines and honor of a warrior society. Subjected to military drills since early manhood, the Spartans became one of the most feared military forces in the Greek world. At the height of Sparta's power – between the 6th and 4th centuries BC – other Greeks commonly accepted that "one Spartan was worth several men of any other state." According to Thucydides, the famous moment of Spartan surrender on the island of Sphacteria, off Pylos, in 425 BC, was highly unexpected. He wrote that "it was the common perception at the time that Spartans would never lay down their weapons for any reason, be it hunger, or danger."